Separation of zinc(II), nickel(II), and cobalt(II) with dithizone based on differences in rates of extraction

Abstract

The extraction constants (K*) for zinc(ll), cobalt(ll), and nickel(ll) were determined for the extraction of the metal ion from an aqueous phase into a chloroform solution of dithizone. The extraction constant for nickel (0.60) was significantly different from that reported by Koroleff (1.2 -3). This difference is attributable to the slow formation of the nickel dithizonate. As Zn(ll), Co(ll), and Ni(ll) cannot be separated by extraction with dithizone without the use of masking agents, the optimum conditions for the separation of the ion pairs Ni-Zn, Zn-Co, and Ni-Co, based on the differences in the rates of formation of the metal dithizonates, were determined. More than 99% of Zn could be extracted while only 2.5% of Ni extracted. The optimum conditions determined for the separation of Zn from Co resulted in extraction of 96% Zn with only 8.6% Co extracting. The separation of Co from Ni was less effective, because of the similarity in extrac-'To whom inquiries should be addressed.

Spectrophotometric Determination of Cobalt(II) Using the Chromogenic Reagent 4,4′-Diazobenzenediazoaminoazobenzene in a Micellar Surfactant Medium

“…The spectrophotometry of micro amounts of cobalt has recently attracted much attention owing to environmental concerns. Various spectrophotometric methods for the determination of cobalt using dithizone, 1 4-(2-pyridylazo)resorcinol (PAR), 2 zincon, 3 6-amino-4-hydroxy-5-(2-hydroxy-4-nitrobenzeneazo)naphthalene sulfoacid, 4 5-(2-amino-4-hydroxybenzeneazo)-o-benzenebromethyl hydrazide, 5 etc., have already been reported. However, most methods are relatively complicated and organic solvent extraction is necessary, usually using a toxic organic solvent such as chloroform.…”

Preconcentration of Cobalt(II) Using Synergistic Extraction with Dithizone and Tributylphosphine Oxide

“…Moreover, the synergism may accelerate the extraction, although the dithizone (H2dz, 3-mercapto-1,5-diphenylformazan) extraction of cobalt(II) is known to be slow. 2 The authors previously succeeded in the preconcentration of cadmium(II) by employing the synergistic extraction with dithizone and trioctylphosphine oxide (TOPO). 3 In that system, however, the phase separation was very time-consuming, and centrifugation was required occasionally.…”